This invention relates generally to a surface treatment apparatus, and more particularly to a surface treatment apparatus capable of detecting the condition of removal of an organic substance, such as a resist, from a wafer of a semiconductor.
In the process of manufacturing a semiconductor, an organic resist film, such as a photoresist, is used as a mask. In order to remove the unnecessary organic resist film after the etching and the doping are carried out, instead of a wet process using an oxidation liquid, there has extensively been used a dry process in which the oxygen atoms in the atmosphere are activated by a plasma, thereby removing the resist film through oxidation. In such a plasma process, a semi-conductor device is exposed to the plasma, and due to a charge-up by the plasma, the semiconductor device is subjected to damage. Therefore, in order to keep such damage to a minimum, it is essential to detect the end point of the organic substance removal treatment, and for this purpose there has been employed a method for detecting gas as disclosed in Japanese Patent Unexamined Publication No. 63-70427.
In such prior art, the removal of an organic substance is carried out in a vacuum chamber, and therefore gas other than the gases related to the removal treatment will not be introduced into the vacuum chamber. Ultraviolet rays/ozone asher (disclosed, for example, in U.S. Pat. No. 3,890,176), in which the removal of organic substances is carried out below the atmospheric pressure, is much more effective than the above prior art. However, since a treatment chamber is not air-tight, the air intrudes into the treatment chamber from the exterior. Therefore, it has been difficult to analyze a change in the gas concentration related to the removal treatment, and for this reason such a process has not been performed.